1 (**************************************************************************)
4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
13 (**************************************************************************)
15 include "basics/star.ma".
16 include "basics/lists/list.ma".
17 include "arithmetics/exp.ma".
19 include "xoa_notation.ma".
24 (* Note: For some reason this cannot be in the standard library *)
25 interpretation "logical false" 'false = False.
28 non associative with precedence 90
31 lemma ex2_1_commute: ∀A0. ∀P0,P1:A0→Prop. (∃∃x0. P0 x0 & P1 x0) → ∃∃x0. P1 x0 & P0 x0.
32 #A0 #P0 #P1 * /2 width=3/
37 definition confluent1: ∀A. relation A → predicate A ≝ λA,R,a0.
38 ∀a1. R a0 a1 → ∀a2. R a0 a2 →
41 (* Note: confluent1 would be redundant if \Pi-reduction where enabled *)
42 definition confluent: ∀A. predicate (relation A) ≝ λA,R.
43 ∀a0. confluent1 … R a0.
47 definition is_false: predicate bool ≝ λb.
52 lemma lt_refl_false: ∀n. n < n → ⊥.
53 #n #H elim (lt_to_not_eq … H) -H /2 width=1/
56 lemma lt_zero_false: ∀n. n < 0 → ⊥.
57 #n #H elim (lt_to_not_le … H) -H /2 width=1/
60 lemma plus_lt_false: ∀m,n. m + n < m → ⊥.
61 #m #n #H elim (lt_to_not_le … H) -H /2 width=1/
64 lemma lt_or_eq_or_gt: ∀m,n. ∨∨ m < n | n = m | n < m.
65 #m #n elim (lt_or_ge m n) /2 width=1/
66 #H elim H -m /2 width=1/
67 #m #Hm * #H /2 width=1/ /3 width=1/
70 (* trichotomy operator *)
72 (* Note: this is "if eqb n1 n2 then a2 else if leb n1 n2 then a1 else a3" *)
73 let rec tri (A:Type[0]) n1 n2 a1 a2 a3 on n1 : A ≝
75 [ O ⇒ match n2 with [ O ⇒ a2 | S n2 ⇒ a1 ]
76 | S n1 ⇒ match n2 with [ O ⇒ a3 | S n2 ⇒ tri A n1 n2 a1 a2 a3 ]
79 lemma tri_lt: ∀A,a1,a2,a3,n2,n1. n1 < n2 → tri A n1 n2 a1 a2 a3 = a1.
80 #A #a1 #a2 #a3 #n2 elim n2 -n2
81 [ #n1 #H elim (lt_zero_false … H)
82 | #n2 #IH #n1 elim n1 -n1 // /3 width=1/
86 lemma tri_eq: ∀A,a1,a2,a3,n. tri A n n a1 a2 a3 = a2.
87 #A #a1 #a2 #a3 #n elim n -n normalize //
90 lemma tri_gt: ∀A,a1,a2,a3,n1,n2. n2 < n1 → tri A n1 n2 a1 a2 a3 = a3.
91 #A #a1 #a2 #a3 #n1 elim n1 -n1
92 [ #n2 #H elim (lt_zero_false … H)
93 | #n1 #IH #n2 elim n2 -n2 // /3 width=1/
99 (* Note: notation for nil not involving brackets *)
101 non associative with precedence 90
104 let rec Allr (A:Type[0]) (R:relation A) (l:list A) on l : Prop ≝
107 | cons a1 l ⇒ match l with [ nil ⇒ True | cons a2 _ ⇒ R a1 a2 ∧ Allr A R l ]